commercial load calc

[stew]

have a commercial calc I need help with. a manicure pedicure spa place. 6 ea 8.2 amp commercial pedicure spas @ 120 v. 2 ea 3/4 hp makeup and exhaust fans @ 208v. 10000 wat water heater @ 208 v. dryer @ 6500 w 208 v. 13 each 3 bulb existing flour. fixture about 1.2 a each @ 120 v.

The existing transformer is 15 kva 42 amps. 120/208 v three pphase I think with the added loads I might need a 25 kva transformer. There is a 125 a 480 volt feed to the existing transformer. Primary feed seems ok but secondary a bit small I think. Any inputs?

 

[haskindm]

You will need to do a COMPLETE load calculation, including lighting load, heat, air conditioning, etc. Just calculating the equipment that you are adding, tells you nothing.

 

[bob]

Stew
Why are you required to use the transformer. What is the std utility voltage?

 

[stew]

This is a large mega-mall cut into small stores. Each store is fed with 125 amps, 480 volts and each has its own transformer. The loads that I have specified are all of the loads in this store.

 

[Smart $]

As haskindm wrote, you will need to do a complete load calculation. For one, lighting is greater of min req'd based on floor area or actual. No way t tell which is greater from your info. Also, what about receptacle loads? I don't see any mentioned...

 

[joe tedesco]

See Annex D and one example related to your questions.

 

[stew]

al of the lighting is exixsting. the rest of the loadsd are as shown

 

[Jljohnson]

Stew, Just because the lighting and receptacles are existing doesn't mean they do not have to be included in a load calc. Based on Sq. footage, you need to come up with the general lighting load, then add 180 VA for each duplex receptacle, show window loads(200VA per lieal ft. 220.14.G), etc. You have not provided enough info for us to help you. FWIW, my gut says the 15 KVA is not enough.

 

[Wes G]

Not as simple as it might look!

Not as simple as it might look!

Stew, some of the questions that come to my mind are these:

1. Since this is a part of of a structure that is already sized for lighting load etc.for its feeders, those factors need not come into play unless this section is isolated by firewalls and this is classified as another service. The question is,are the 13 fixtures you site and the loads you specify the only loads on this transformer? If so they total about 13KVA on a three phase 208V transformer when totaled, and the 120V loads are ballanced, in which case 15KVA should be adaquate.

2. Does the main buildings power supply any loads in this stores area?

3. What are the prospects for future expansion?

4.It looks like your feeders are probably sized for 125A which gives me a three phase potential of about 104KVA. Is this smaller transformer properly fused etc.?

___________________
Wes Gerrans
Instructor
Northwest Kansas technical College
Goodland, KS